The Electrodacus SBMS thread (SBMS0, DSSR50, etc)

[Geriakt]

If you are using or planning to use the SBMS0 and you have sketched out a diagram or schematic, or have pictures of your setup please share it here. We are a small group of folks using or planning to use this BMS, and there isn't much info on it available online, if we can get a handful of examples in one place, it'll go a long way to helping others with their designs, and we can learn and borrow from eachother!

I am using 2 SBMS0s for a 24 volt 2 Tesla Module system. I use a Victron Multiplus 24/3000 70-50, 1150 watts PV connected to a Epever 40 amp MPPT.
Tom

 

[Dzl]

To start things off,

Here is a very early working draft of the system I am designing. It is very likely that there are errors and omissions, and very likely that it will change substantially between now and the final version.



This is a vehicle based system. Some of my guiding design principles/objectives are:

• Maximum efficiency
• Minimal no-load consumption
• Modularity
• Maximize partial Shade tolerance/performance
• Flexible/wide range of operation
• Open Source, Open Hardware, and DIY where possible
• Layered protection and control
• Data! I ❤ pretty charts and graphs
• And of course cost/value

Edit: I also made a diagram to make sense of my diagram (not even joking... ), in case the full diagram is too overwhelming cluttered. The basic layout is Top: charge sources, Middle: battery core system + primary distribution, Bottom: load distribution.

Spoiler: diagram of the diagram...

 

[dgjonesy]

To start things off,

Here is a very early working draft of the system I am designing. It is very likely that there are errors and omissions, and very likely that it will change substantially between now and the final version.



This is a vehicle based system. Some of my guiding design principles/objectives are:

• Maximum efficiency
• Minimal no-load consumption
• Modularity
• Maximize partial Shade tolerance/performance
• Flexible/wide range of operation
• Open Source, Open Hardware, and DIY where possible
• Layered protection and control
• Data! I ❤ pretty charts and graphs
• And of course cost/value

Nice drawing. What tool did you use to create it ?

 

[Dzl]

I am using 2 SBMS0s for a 24 volt 2 Tesla Module system. I use a Victron Multiplus 24/3000 70-50, 1150 watts PV connected to a Epever 40 amp MPPT.
Tom

Thank you! Super helpful, I need some time to digest though

Spoiler: I rotated and enhanced your images a bit to make them bit easier to read

 

[ianganderton]

To start things off,

Here is a very early working draft of the system I am designing. It is very likely that there are errors and omissions, and very likely that it will change substantially between now and the final version.



This is a vehicle based system. Some of my guiding design principles/objectives are:

• Maximum efficiency
• Minimal no-load consumption
• Modularity
• Maximize partial Shade tolerance/performance
• Flexible/wide range of operation
• Open Source, Open Hardware, and DIY where possible
• Layered protection and control
• Data! I ❤ pretty charts and graphs
• And of course cost/value

Are there any problems associated with connecting/disconnecting via relay the batteries from the MPPT SCCs?

Why use several MPPT SCCs?

Again super neat drawing what software did you use?

 

[Dzl]

Nice drawing. What tool did you use to create it ?

Diagram created with Draw.io, its my first time using it but I really like it so far. Its pretty easy to work with having layers is great, putting each module or circuit in its own layer adds a lot of flexibility, and makes it easier to focus on just the relevant components. For example, the diagram I posted above has all the layers but its pretty cluttered, with just a few clicks I can see:

Spoiler: Just the charging system:

Or

Spoiler: Just one of the solar modules:

The individual components were either borrowed and modified from other diagrams (especially Victron's) or created in GIMP (free open source photoshop like program).

 

[Dzl]

Are there any problems associated with connecting/disconnecting via relay the batteries from the MPPT SCCs?

So I suppose there are two questions embedded in this question:

First, is it safe for the battery protect to be used in this manner?

As far as I know, this is as acceptable but non-conventional way to use the battery protect (see this thread) more specifically @Justin Laureltec's response. But its something I would confirm with Victron before moving forward if I stick with this design.

Second, is it safe for the charge controllers to be disconnected from the battery while connected to the PV panels?

Conventional wisdom not so long ago was that this was not a good idea. However, this perception seems to be shifting (see Will's thread "Trying to destroy my SCC's, I can't") Victron's documentation doesn't caution against this or otherwise indicate that this is a bad idea or would void their warranty. See post #42 and #43 for more info and a good explanation from Justin, that pretty much puts the issue to rest in my eyes, at least with Victron controllers.

Why use several MPPT SCCs

This is a practice seen mostly in the marine world where rigging, sails, etc can really screw with solar output. I'm incorporating it as part of my strategy to mitigate partial and unpredictable shading. 1:1 panel to MPPT ratio means partial shade on 1 panel has no effect on the others, and each controller can determine the maximum power point specific to the panel hooked up to it. I understand the theoretical benefits of this, I have no idea what the real world gains will be, and haven't been able to find much data on it, but its often recommended in the marine world and the difference in price between 3 small controllers or 1 larger controller is pretty negligible ($355 for 3x 75v/15a, or $325 for 1 x 100v/50a) so I'm willing to pay a little more for the theoretical benefits.

Its part of my broader attempt to mitigate partial shade

1. Use panels designed to perform better in partial shade (like REC Peak or Alpha panels or Sunpower X series or P series)
2. Use higher voltage panels and minimize or eliminate series connections
3. Multiple MPPT controllers
4. Possibly make one of the 3 solar 'modules' portable so if I'm camped in the shade I can set up one module in the sun away from the vehicle. Probable won't end up doing this, but its an option.

If you, or anyone else is interested, I have started several threads (see here) on partial shade performance, as questions have come up and as I've learned.


As I mentioned, this is a super early working draft of the system I'm designing, so a lot will probably change, and I very much welcome questions, criticism, tire kicking, recommendations, and second guessing

 

[Dhowman]

So I suppose there are two questions embedded in this question:

First, is it safe for the battery protect to be used in this manner?

As far as I know, this is as acceptable but non-conventional way to use the battery protect (see this thread) more specifically @Justin Laureltec's response. But its something I would confirm with Victron before moving forward if I stick with this design.

Second, is it safe for the charge controllers to be disconnected from the battery while connected to the PV panels?

Conventional wisdom not so long ago was that this was not a good idea. However, this perception seems to be shifting (see Will's thread "Trying to destroy my SCC's, I can't") Victron's documentation doesn't caution against this or otherwise indicate that this is a bad idea or would void their warranty. See post #42 and #43 for more info and a good explanation from Justin, that pretty much puts the issue to rest in my eyes, at least with Victron controllers.

I agree. Some SCCs, and even SBMSn where n>0 ... you cannot disconnect battery before you disconnect panels. Well, you could, but you fry the SCC. I do not believe this is true with Victron MPPT. Peeps do this all the time with them (and other SCCs) to no ill effect. Def worth confirming if this is possible for your specific model before doing this.

This is a practice seen mostly in the marine world where rigging, sails, etc can really screw with solar output. I'm incorporating it as part of my strategy to mitigate partial and unpredictable shading. 1:1 panel to MPPT ratio means partial shade on 1 panel has no effect on the others, and each controller can determine the maximum power point specific to the panel hooked up to it. I understand the theoretical benefits of this, I have no idea what the real world gains will be, and haven't been able to find much data on it, but its often recommended in the marine world and the difference in price between 3 small controllers or 1 larger controller is pretty negligible ($355 for 3x 75v/15a, or $325 for 1 x 100v/50a) so I'm willing to pay a little more for the theoretical benefits.

Its part of my broader attempt to mitigate partial shade

1. Use panels designed to perform better in partial shade (like REC Peak or Alpha panels or Sunpower X series or P series)
2. Use higher voltage panels and minimize or eliminate series connections
3. Multiple MPPT controllers
4. Possibly make one of the 3 solar 'modules' portable so if I'm camped in the shade I can set up one module in the sun away from the vehicle. Probable won't end up doing this, but its an option.

If you, or anyone else is interested, I have started several threads (see here) on partial shade performance, as questions have come up and as I've learned.


As I mentioned, this is a super early working draft of the system I'm designing, so a lot will probably change, and I very much welcome questions, criticism, tire kicking, recommendations, and second guessing

So, a few things jump out at first glance:

1. Maybe I'm missing something, but I don't see how paralleling 3 panel/mppt combos is any different than paralleling 3 panels to one larger MPPT when it comes to shading. Sum of the 3 smaller power points would be equal to the power point of the one larger one, no? And total amps produced by those 3 panels and seen by 3 MPPTs isn't gonna be different than what one MPPT sees regardless of how much or how little shade is hitting them. And if that larger one had remote on/off, you don't need the BP. Only advantage I see is that if that one MPPT has a problem, you have no solar. You have some redundancy with the 3-MPPT setup.

2. Also, just want to make sure you know that you've defeated the isolation of your DC-DC charger by grounding your NEG bus to chassis. It's, essentially, a non-isolated DC to DC charger at that point. Not sure what the ramifications (or benefit) of doing that is, esp if you eventually hook all that up to a generator or shore power too and have everything running at the same time.

3. Also, what's the use case for 2 BPs on your DC loads line (w 2-24V and 2-12V DC panels = 4 distribution panels)? What's controlling the 2nd one to your "Switched Distribution?" "Unswitched Distribution" is switched by the first BP, is it not?

4. Why the fuse/switch combos? Why not just breakers performing both functions? One switch for everything coming to the battery shunt? You might want the flexibility of having breakers on all those individual lines (vs one switch/multiple fuses).

Overall, it seems, maybe, that the total # of devices here could be minimized to make for a simpler/easier to troubleshoot system that satisfies the same requirements. Or maybe I just don't understand the requirements part well enough.

 

[Dhowman]

1. Maybe I'm missing something, but I don't see how paralleling 3 panel/mppt combos is any different than paralleling 3 panels to one larger MPPT when it comes to shading. Sum of the 3 smaller power points would be equal to the power point of the one larger one, no? And total amps produced by those 3 panels and seen by 3 MPPTs isn't gonna be different than what one MPPT sees regardless of how much or how little shade is hitting them. And if that larger one had remote on/off, you don't need the BP. Only advantage I see is that if that one MPPT has a problem, you have no solar. You have some redundancy with the 3-MPPT setup.

Caveat to this is, if your panels aren't all the same voltage, you could benefit by matching w multiple/different MPPTs.

 

[Dzl]

I love this! Feedback like this is why I love this forum. All very good points and questions. You've touched on a lot of points that I've gone back and forth on, and highlighted isssues I hadn't fully considered. I'm not going to respond to it all here as I don't want to distract from the focus of this thread, but I started this thread here to discuss and explain my design as it evolves, and I'll address the points you made here in that thread.

 

[Dzl]

Really feel Dacian is missing an increasing market, by not offering a 48v version. As things head to 'all electric' the world over, larger battery banks are going to be sought. :-(

The point is Kernel, this guy is onto something with this design....extending the range has the potential to open up whole new markets to him. Maybe he is simply happy with production as is....something to be said of stay small, stay in control.

I'm dragging up an old part of the conversation, but I came across more explanation as to why Dacian has not built a 48V version in the comments section of wills video on the SBMS0.

The product, help and support are excellent but like most setting up an off-grid home system and integrating it with victron products not supporting 48V has meant that non of his products are usable. All the other big solar mppt/inverter manufacturers would all be 48V in an off-grid house application. So disappointing!

I do not design anything that exceeds 50V DC open circuit voltage for safety reason and to stay in the Low voltage standard that is set at 50 or 60V DC around the world. As SBMS0 can handle 750A and can deal with up to 30kW PV array I do not see a limitation in most systems. I even fully heat my house with 24 to 30V DC system so there is not a big advantage to 48V other that some savings on wires but that from the total cost of the system is not much and the extra safety of lower voltage is worth it for me. I designed this for my own use I'm not in any way a big manufacturer is more of a hobby. I do understand that you are already invested in 48V so you need to stay with that. Tow SBMS0 in series can control a 48V system but is not at all an elegant solution so not something I recommend.

 

[Dzl]

Couple new youtube videos on the SBMS0:

 

[Dhowman]

Couple new youtube videos on the SBMS0:

Liked the 2nd vid. First one I've seen that included DSSR20 in the demo. First vid was a little distracting, worrying he was going to stand up. #pants? lol

 

[sharpey]

Hey Folks, I got inspired by the schematic that DZL posted about using the SBMS0 on a 24V off grid system. I'm planning something similar, spit 12-24V system, but on a sailboat. Would very much welcome comment and criticism on my "alpha" schematic... See the pdf if the zoom sucks. Thanks everyone!

 

[Dzl]

Hey Folks, I got inspired by the schematic that DZL posted about using the SBMS0 on a 24V off grid system. I'm planning something similar, spit 12-24V system, but on a sailboat. Would very much welcome comment and criticism on my "alpha" schematic... See the pdf if the zoom sucks. Thanks everyone!
View attachment 11802

Looks good at first glance!

You may want to consider locating a fuse on the positive line where it branches off just before the solar shunt, depending on the distance between that point and the branch fuses after the switch. I'm not necessarily recommending it and i'm far from an expert, but it is something I would be considering. You do have the MRBF fuse on your main battery negative, so the fuse on the + side maybe isn't exactly necessary, my design has the fuse on the negative as well, but I"m still not 100% comfortable with that arrangement personally.

You might also want to double check ABYC code (if you are located in the US), it requires a fuse within 7" of the battery, there are a couple exceptions to this. I'm not sure if fusing the negative side meets this rule or not.

Otherwise, looks good.

What 24v to 12v converters are you using?

 

[sharpey]

Looks good at first glance!

You may want to consider locating a fuse on the positive line where it branches off just before the solar shunt, depending on the distance between that point and the branch fuses after the switch. I'm not necessarily recommending it and i'm far from an expert, but it is something I would be considering. You do have the MRBF fuse on your main battery negative, so the fuse on the + side maybe isn't exactly necessary, my design has the fuse on the negative as well, but I"m still not 100% comfortable with that arrangement personally.

You might also want to double check ABYC code (if you are located in the US), it requires a fuse within 7" of the battery, there are a couple exceptions to this. I'm not sure if fusing the negative side meets this rule or not.

Otherwise, looks good.

What 24v to 12v converters are you using?

Thanks for your reply. I see what you mean about the fuse, but I'm hoping all these components (+ve shunts, switch & fuses are as close to the batteries as I can make them... hopefully less than 1 metre... Can't measure at the moment since we're all stuck at home! I'll bear that in mind.

Forums are great! Whenever I need to learn about stuff like this, forums are where it's at... So glad I found this place... I have grown to prefer the advice of many "enthusiasts" over 1 or 2 experts.... We're all smart enough to figure most things out this way... Well, at minimum to get us to a stage where we cold show a diagram that's 90% of the way there to a certified tech, and not pay a fortune for advice on that last 10% of fixes/optimisations.

I reckon I'll send my diagram off to the SBMS0 guy with a couple of questions and see what I get back. I'm really excited about the robustness of this setup... which I think is enhanced by the modularity... easy to carry spare battery protect modules if I'll be going far from home.

I found Aliexpress specials for the 24-12 converters... https://www.aliexpress.com/item/32778224644.html?spm=a2g0s.9042311.0.0.4e164c4dzxW51U . With any luck they'll perform as advertised.. I've had pretty good luck with AliExpress in the past... usually if the seller responds within an hour of a question being asked, and feedback is generally above average, I tend to "take the chance".

Will be watching your progress with interest... Cheers!

 

[Dzl]

Anyone using the DSSR20 controllers with 'diversion' capability? These are the controllers that take over the role of the older DMPPT diverting excess PV power to be used for heating water or a radiant floor, or stored in thermal mass.

Lately I've been thinking about trying to figure out how to utilize excess PV for water heating purposes, the DSSR20 with diversion seems like a practical way to accomplish this, but I can't find any info on it.

 

[sharpey]

To start things off,

Here is a very early working draft of the system I am designing. It is very likely that there are errors and omissions, and very likely that it will change substantially between now and the final version.



This is a vehicle based system. Some of my guiding design principles/objectives are:

• Maximum efficiency
• Minimal no-load consumption
• Modularity
• Maximize partial Shade tolerance/performance
• Flexible/wide range of operation
• Open Source, Open Hardware, and DIY where possible
• Layered protection and control
• Data! I ❤ pretty charts and graphs
• And of course cost/value

Edit: I also made a diagram to make sense of my diagram (not even joking... ), in case the full diagram is too overwhelming cluttered. The basic layout is Top: charge sources, Middle: battery core system + primary distribution, Bottom: load distribution.

Spoiler: diagram of the diagram...

View attachment 11261

Ok, I have a question here. I note you've got your B2B charger going through your battery shunt and not your PV shunt. Is there a reason you can't wire the B2B charger to the PV shunt? That way you'd avoid errors with the sbms0 calculating remaining charge no? Apologies if this has been answered (I recall reading it somewhere) just can't remember what the conclusion was.

I've put my money down on an SBMS (thanks to you, and Dacian's superb attitude when it comes to walking newbies through via email)...

Cheers!

James

 

[sharpey]

I re-read the thread (yes I am committed lol)... The earlier post was mentioning that an inverter charger should connect at the battery shunt, not the pv shunt... That I can understand... But since a B2B is only charging, it should be able to live with the PV on the PV shunt no?

Just thinking out loud here.

Cheers,

James

 

[Metamorfos]

I already have a SBMS0. I want to capacity test any new batteries I order from China. Is using the SBMS0 a viable option to control this process? I would charge to full capacity using my solar panels (which I also already have). Once all batteries are charged, I would use my inverter to put a load on the pack and let my SBMS0 handle the rest and deduct my capacity from that.

I don't feel like buying a charger I would only use a couple of times if I can pull of the test with my SBMS0, solar panels and a load on my inverter.

 

[Dzl]

Ok, I have a question here. I note you've got your B2B charger going through your battery shunt and not your PV shunt. Is there a reason you can't wire the B2B charger to the PV shunt? That way you'd avoid errors with the sbms0 calculating remaining charge no? Apologies if this has been answered (I recall reading it somewhere) just can't remember what the conclusion was.

I've put my money down on an SBMS (thanks to you, and Dacian's superb attitude when it comes to walking newbies through via email)...

Cheers!

James

So you bring up a good point that I probably should've touched on earlier.

First, I should clarify, I'm still not 100% confident in my understanding, but I pretty sure I'm on the right track. As I understand it, Dacian designed primarily with a single charge source in mind, solar. With a single charge source, the dual shunt model works perfectly, you can track what your PV array is producing via the PV shunt, and track overall current in/out via the battery shunt (and use data from the two shunts to deduce load current).

Now the SBMS can handle more charge sources, but then you have a decision to make.

1. Connect the additional chargers after PV shunt and sacrifice accurate PV array data, but preserve accurate current in/current out data (net current and SOC would still be accurate)
2. Connect the additional chargers before the PV shunt (with the loads) and sacrifice accurate current in/current out but preserve accurate PV data (net current and SOC would still be accurate)

So basically in either case, SOC and net current will be accurate, and but you have to choose whether you want the shunts to measure PV and 'everything else', or chargers and loads. Initially i was planning 'chargers and loads', but the more I thought about it the more I thought that accurate PV data would be much more useful than lumping data from all the chargers together.

By placing the B2B with the loads before the PV shunt, my PV data will be accurate, my SOC and net current will be accurate, but when the vehicle is running I won't be able to know exactly how much current is flowing in vs out.

 

[Dzl]

^^ was that clear at all? That was a pre-coffee reply, if it still doesn't make sense, or if you think I misunderstood something, I'm happy to discuss further

 

[sharpey]

^^ was that clear at all? That was a pre-coffee reply, if it still doesn't make sense, or if you think I misunderstood something, I'm happy to discuss further

Hey Hey,

Yes, that does make sense. Read it pre-coffee also lol.... I'm guessing you are keen on being able to track your solar efficiency? I have plenty of time to think this over, but on a boat, the solar I've got is the solar I've got... hard to optimise... as I can't move the panels. As such it would make more sense (in my head) to favour option 1.



Cheers,

James

 

[Dzl]

Hey Hey,

Yes, that does make sense. Read it pre-coffee also lol.... I'm guessing you are keen on being able to track your solar efficiency?

Yeah, at least that's my current thinking. My thinking is that shore power and/or the B2B charger should be pretty stable and predictable inputs, I won't need a granular view of the data in those situations, and I probably won't be paying much attention in the situations where I'm using one of those charge sources (i.e. driving, or plugged into shorepower). But being able to see a years worth of PV data seems super useful. And 80% or more of the time PV would be my only charge source anyways. But I'm still thinking through situations where it would be useful to have accurate input output data.

The important takeaway is that either way its configured, it will have all of the capabilities that any other single shunt system would have + the extra capabilities based on where the charge sources are hooked up.

 

[sharpey]

Cool. I get what you mean here. I'm in the same situation. Solar will likely be the only charge source 80% of the time. 24v 280ah with around 690w of solar from 2 345sunpower panels. It'll take about 2-3days of tropical sun to charge the bank from 10%, but I don't forsee needing to run the bank that low, that often. Most of my sailing is day sailing with occasional trips. That's why I'm not even bothering sorting out the b2b charger just yet.

Cheers,

James